Saturday, November 7, 2009

When Engineers Get Bored...

...they complicate what should, or even used to be, something simple.

Case in point, a 2006 BMW 325i that I replaced the rear brake pads on yesterday. BMW is among several manufacturers that incorporate wear sensors into their brake systems, which in itself is not a bad thing. It's really simple, actually: a soft plastic piece with a simple loop of wire in it clips into one inner brake pad at each end of the car. When the pad wears, this piece hits the rotor, and eventually wears through. Once the wire loop either
a) contacts the rotor and grounds against it, or
b) wears through and opens the circuit,

it illuminates a warning light on the dash. Much more effective than squeaker tabs, the circuit "latches" once activated to prevent the light flickering on and off as the pad touches the rotor. So far, so good.

(Photo of E90 cluster from user "NoKids" at - )

This is where it all goes wrong. In older BMWs, you'd replace the pads and the sensor (sensors are about $35 each, no big deal), then you leave the key "on" with the engine off for 10 to 60 seconds to reset the light. Not this one. In this version, the "E90" model, things are a little more complicated, and don't look for the procedure in the manual or in the Mitchell or Alldata information most shops use. You won't find it.

Here, courtesy of an online BMW fan forum (and much surfing), is the final operation required - unless you have a factory BMW scan tool:

- insert key fob into dash receptacle.
- push "Start" button, but do not have your foot on the brake at the time (this puts the car in "run" but not running).
- wait for "Service" warning message to go out in message centre, replaced by the clock and odometer display.
- immediately push and hold "BC" button on signal stalk until "Service" indicator returns.
- use up and down toggle switch on signal stalk to highlight the desired service reminder.
- push and hold BC button until "Reset" appears in display.
- release and reapply BC button until a rotating clock symbol appears and then goes out.
- you may now exit the menu, turn off the car, or restart it as desired. Test drive it to ensure that the service warning is actually is out.

Hey, that was easy! I'd probably have figured it out on my own eventually - you know, an infinite number of monkeys at an infinite amount of typewriters, and so on...

No comments:

Post a Comment